Shift bar housing assemblies for mechanical change gear transmissions comprising a plurality of generally parallel, independently axially movable shift bars to be selected and axially moved to effect engagement/disengagement of a particular gear ratio are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 2,951,392; 4,455,883; 4,575,029; 4,567,785 and 4,584,895, the disclosures of all of which are hereby incorporated herein by reference.
Typically, such shift bar housings are manually controlled and operated by a shift finger fixed to a directly mounted shift lever or to the cross shaft of a remotely controlled shifting mechanism. Interlock mechanisms are usually provided to prevent movement of more than one shift rail at a time from the axially centered or neutral positions thereof.
Automatic and semi-automatic mechanical transmissions based upon generally standard mechanical transmissions provided with electric/pneumatic actuators controlled by a control unit are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 4,648,290 and 4,361,060, the disclosures of which are hereby incorporated herein by reference.
Automatically controlled X--Y type shifting mechanisms wherein a shift finger is automatically moved in the X or rail selection direction and then in the Y or gear engagement/disengagement direction are known in the prior art as may be seen in reference to U.S. Pat. No. 2,931,237, the disclosure of which is hereby incorporated by reference.
Shift bar housing assemblies utilizing pressurized fluid actuated pistons and the like to control each shift rail in an automatic or semi-automatic mechanical transmission are known in the prior art as may be seen by reference to U.S. Pat. No. 4,445,393.
The prior art shifting mechanisms for providing automatic and/or semi-automatic shifting of mechanical change gear transmissions normally utilized with direct and/or remote manual shifting mechanisms were not totally satisfactory as substantial modification of the standard shift bar housing assembly was required; complicated and costly valving and support equipment such as reservoirs, driers and filters, and/or fluid/electrical connections were required, the controls were complicated and/or expensive to manufacture, assemble and/or repair; commonly required the availability of air, and/or the controls did not provide a rapidly and positively obtainable neutral position and a reliable indication device therefor.